1. Field of the Invention
The present invention relates to a vehicle velocity detecting device which can detect the velocity of a vehicle and display it on e.g. an instrument panel by using values detected by wheel speed sensors arranged on respective wheels in the anti-lock brake control apparatus.
2. Description of the Related Art
In the conventional vehicle, it has been generally carried out to detect a rotating speed of an output shaft of the transmission apparatus, in other words, an average of rotating speeds of driving wheels and display it on e.g. a speed meter of the instrument panel, as "vehicle velocity". While, the vehicle velocity detecting device disclosed in Japanese Unexamined Patent Publication (kokai) No. 9-272421 detects the vehicle velocity by processing signals generated from the rotating speed sensors arranged on respective wheels in the anti-lock brake control apparatus.
Now, although the above-mentioned earlier vehicle velocity detecting device adopts an average of driving wheels' speeds detected by the wheel rotating speed sensors of the anti-lock braking control apparatus as the vehicle velocity, the device has a problem that the wheel speeds detected by the wheel rotating speed sensors may contain undesirable noises, different from the rotating speed obtained by the rotating speed sensor detecting revolutions of the output shaft of the transmission apparatus. In detail, it is believed that the occurrence of noises originates in the vibrations of disc rotors and brake pads of the wheels, the magnetic field generated from cables embedded in the ground a road, or the like. Consequently, under a specific condition, the vehicle velocity detecting device incorrectly detects the wheels speed which is apt to be normally larger than the actual rotating speed of the wheel.